Cactaceae family is an important plant of Arid and Semi-Arid Lands (ASALs) of the world. It is useful for ornamental (Cereus peruvianus and Thrixanthrocereus blossfeldiorum), food, fodder and industrial production (Opuntia spp.). The objective of this study was to characterize and determine the distribution of cactus species in two ASAL zones of Kenya (Rift Valley and Eastern).Sixty nine distinct populations of cactus were characterized in-situ using a list of descriptors by the International Union for the Protection of New Varieties of Plants (UPOV). Results indicated that eight species namely, Opuntia exaltata, Opuntia monacantha, Opuntia ficus-indica, Opuntia stricta, Thrixanthrocereus blossfeldiorum, Euphorbia abyssinica, Euphorbia ingens and Cereus peruvianus were present in Kenya. Opuntia ficus-indica was the most diverse and was found in four of the five counties studied. Euphorbia abyssinica was found in four counties while Opuntia stricta and Thrixanthrocereus blossfeldiorum were found in a single county each. The results revealed morphologically a significant diversity among cactus species in Kenya. Further research is needed through molecular characterization and to cover the entire country to identify other species available in these areas and their mode of distribution as well as their productivity to influence the choice species for utilization.